Map shows Calif. areas prone to landslides

California has a new resource to show what's happening beneath our earthquake-prone ground. A map showing landslide risks is the first of its kind for the state.

The coastal mountain region from San Francisco to Los Angeles is most at risk. The map is color-coded to identify the areas where there are steep slopes and weak rocks. That combination, indicated by dark red on the map, makes a region highly susceptible to a landslide, according to geologists.

There are quite a few of those areas in Southern California. A landslide closed a 150-foot stretch of Pacific Coast Highway in Dana Point earlier this year when a hillside gave way after heavy rain.

Around the same time, a major landslide left four homes red-tagged in San Clemente. Their patios were teetering over an edge overlooking a golf course.

In 2005, a landslide in La Conchita in Ventura County killed 10 people when a massive section of the earth came down and buried some homes. Thirteen homes were destroyed and 23 were damaged.

Geologists say the new mapping technology gives unprecedented detail.

"It took a lot of computer time to do that type of calculation, so it's very accurate for the entire state. At the same time, we folded in some of the best digital geological mapping that was incorporated into it," said Timothy McCrink of the California Geological Survey.

Landslides in California have killed 100 people in the last 25 years. Geologists say that they also want to look at what triggers landslides, such as rainstorms and earthquakes. They want to create potential hazard maps as well.